This invention relates to power supply apparatus for a fusion joining apparatus, which supply is capable of flexible application and convenient use.
Many different methods and apparatuses exist for fusion joining polyethylene pipe, such as with electrofusion fittings or induction fusion fittings. In conventional electrofusion methods, a pipe coupling or other fitting normally has a wire coil moulded within the coupling or other fitting. Electrical leads, contacts or electrodes are often mounted on an external portion of the coupling body, for electrical contact access. In a typical conventional electrofusion procedure for axially joining two pipes, each pipe end portion is cleaned (for example by scraping) and then positioned within a coupling. A clamp is often used to secure or hold the pipe with respect to the coupling. Power is supplied directly to a wire coil moulded within the coupling. The wire coil then transfers heat generated by resistance heating to the polyethylene material and fuses the coupling material directly to the pipe material.
In conventional induction fusion procedures, a heater element is moulded within the coupling or other fitting. The coupling provides no direct access to external contacts or electrodes electrically connected to the heater element. Current flow through the heater element is generated by induction from a primary coil within an application tool that is positioned around the coupling or other fitting. Normally, a high frequency current is delivered to the application tool for a predetermined time period. A primary coil within the application tool is energised and then induces a secondary current within the heater element. The temperature of the heater element increases to a generally constant value and then the polyethylene or other plastics material surrounding the heater element fushion bonds the polyethylene or other plastics material of the pipe and the coupling or other fitting.
The use of induction heating in heat fusion fittings is disclosed, for example, in Ser. No. WO080/02124.
In many conventional processes associated with either electrofusion or induction fusion heating, the power delivered to the wire coil of an electrofusion fitting or a heater element of an induction fusion fitting, necessitates relatively heavy gauge or large cables that must be relatively short, due to the high current and high frequency power waveform transmitted through the cables. Thus, it is often necessary to position the power source relatively close to an installation site or fusion site. Quite often significant amounts of labour and time are necessary to deliver power requirements demanded by the installation tool.